Optical fiber connectors and splicing devices are an important part of substantially any optical fiber communication systems. For instance, connectors or splicing devices may be used to join segments of fiber into longer lengths or to connect fiber to active devices such as radiation sources, detectors, or repeaters, or to passive devices such as switches or attenuators. Considering that a core of multimode optical fiber is approximately 50 microns in diameter and that of single mode fiber is approximately 8 microns, the connection or splicing is no small task.
With respect to multimode fibers for which, due to their relatively large core diameter, alignment to within a few microns is generally acceptable, an alternative type of splicing device has been used. An example of such a multimode fiber splice utilizes two drawn glass capillary tubes or ferrules that serve to hold two fiber end portions and allow alignment of the ends by means of an alignment sleeve. Even though such connectors have been found frequently to give satisfactory results with single-mode fibers, it is not always easy to achieve very low loss connection with these type splicing devices. As used herein, a very low loss connection is defined as connections having a loss of the order of 0.1 dB or less.
The making of single-mode connections in the prior art typically has involved the active alignment of the fiber ends. Prior art methods comprise translating one fiber end relative to the other, typically by means of a precision stage, until maximum energy coupling across the gap between the fiber ends is observed, for example, by means of a remote detector. Such procedure is both difficult to carry out in the field and requires highly skilled personnel.
A somewhat recent entry into the field of optical fiber splicing devices is one which is commonly referred to as a rotary splice. The splicing device is disclosed in commonly assigned U.S. Pat. No. 4,545,644 which issued on Oct. 8, 1985, in the names of G. F. DeVeau, Jr. and C. M. Miller. Generally, the rotary splice device comprises two capillary cylinders and preferably three alignment rods in fixed radial and axial relationship to each other. The alignment rods are generally cylindrical in shape, with typically two of them including a offset area that extends from one end over a substantial fraction of the length of the rod. In such a rotary splicing device, it is the presence of these suitably placed offset areas which allows alignment of the fiber ends to within exceedingly close tolerances.
Notwithstanding the availability of the above-described splicing devices, the search for a reliable optical fiber splicing device has continued. Sought after is a splicing device that is relatively simple and easily installed in the field, is rugged, has acceptable temperature cyclability, and does not require the fiber ends to be subjected to time-consuming polishing procedures.
In all the above-described connectors and splicing devices, cost is an important consideration. It has long been desired to provide a low cost optical fiber splicing device. Also, the splices which are achieved with many of the prior art devices require the use of adhesive materials or gels which require curing. It would be most desirable to have available a mechanical splice which does not require the use of materials to be cured.
An additional variation of the existing three-rod rotary splice comprises three fully cylindrically shaped rods instead of including some rods having a offset surface. However, such splicing devices have a problem of orienting and maintaining the desired physical relationship between each of the rods and the fiber. The sought-after splicing device therefore should include adequate securing means to easily and effectively align and hold each of the rods as desired relative to the fiber ends being spliced.
What is desired and seemingly not available in the prior art is a relatively low-cost, mechanical optical fiber splicing device which includes securing means to properly orient three fully cylindrical rods relative to the fiber ends being spliced. The sought-after splicing device and rod-securing means should be one which is simplistic in structure yet one which provides a reliable relatively low loss and relatively low return loss splice connection.